Strength Estimation Method of Ship Side Structures Subjected to Hard Bow Collision

Abstract

In the collision of hard and sharp bows breaking of ship side structures starts from the collided point of bow, while in the collision of soft and rounded bows breaking is likely to start from the supported point such as bulkhead or transverse web frame. In the case of breaking from collided point stretching of ship side structures is followed by crack propagation, so absorbed energy should be evaluated in consideration of crack propagation.In this paper to develop an evaluation method for breaking from collided point, double hull panel models, which are typical as ship side structures of VLCC, were destructed with the indentation of rigid bow model which was pushed dynamically as well as statically. In the first crack initiation condition was investigated by FEM simulation using fine mesh solid element models and crack initiation was found to be estimated with the ductile damage parameter which consists of equivalent plastic strain and stress triaxiality. Then crack propagation condition was investigated by FEM simulation using coarse mesh shell element models. It was found that reduction of the reaction force due to crack propagation could be simulated by finding the elements adjacent to the crack and reducing the failure strain for those elements.